1. Technical Field
The present application relates to an imaging apparatus which is capable of measuring the distance to an object, an imaging method, and a semiconductor integrated circuit.
2. Description of the Related Art
Known methods for measuring the distances to a plurality of objects included in a scene to be captured (hereinafter, “image capturing scene”) include an active method and a passive method. The active method includes calculating the distance based on the time counted till a reflection wave of emitted infrared, ultrasonic wave, or laser light returns, calculating the distance based on the analysis of pattern light at the time of laser irradiation, etc. Such methods are in general capable of detecting the distance with high accuracy.
According to the passive method, the distance is calculated based on image information of an imaged object. In recent years, the resolution of image sensors is remarkably improving so that, in general, the distance can be calculated with high spatial resolution so long as the computational complexity can be dealt with. Also, high speed imaging of an object enables calculation of the distance with high temporal resolution. Further, in an imaging apparatus, such as a camera, the distance to an object can be measured inexpensively, without adding any direct member for distance measurement, as compared with the active method.
One of known passive methods is Depth from Defocus (hereinafter, referred to as “DFD”) in which the distance is measured based on a blur of an image which is caused by variation of the focus (focusing position). According to this method, the distance can be measured from a small number of images, without requiring a plurality of cameras as explained, for example, following documents:    Patent Document 1: Japanese PCT National Phase Laid-Open Publication No. 2009-505104;    Non-patent Document 1: A. Pentland, “A New Sense for Depth of Field”, IEEE Trans. Pattern Analysis and Machine Intelligence 9 (4) 1987 523-531; and    Non-patent Document 2: M. Subbarao, “Parallel Depth Recovery by Changing Camera Parameters”, 2nd International Conference on Computer Vision, (1988).